| 摘要 |
A fluid control system for actuating a conventional power steering unit including a priority valve. The priority valve includes an inlet chamber connected to a pressure source, a priority outlet chamber connected to the steering unit, and a secondary outlet chamber connected to a secondary motor. The priority valve includes a valve spool slidable in a bore. One end of the bore with the spool forms a servo chamber which has a compression spring which urges the spool in one direction, and the other end of the bore and spool forms a servo chamber which acts in opposition to the first servo chamber. Each servo chamber is connected to the inlet pressure through an orifice in the valve spool which results in a rapid response time for moving the valve spool since the fluid travels only a short distance and since the fluid circulates it remains hot. There is a small logic control circuit flow across the priority valve and the steering valve for the steering unit. The logic flow passes across an orifice in the valve spool into the servo chamber with the compression spring, then across a second orifice before it flows into the steering flow downstream of a variable orifice in the steering valve. By reason of the two orifices in series, the spool of the priority valve can use a lower spring rate since a majority of the pressure drop will be taken downstream of the steering unit variable orifice.
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